package org.apache.solr.spelling;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.apache.lucene.analysis.Token;
import org.apache.solr.common.params.CommonParams;
import org.apache.solr.common.params.ModifiableSolrParams;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.handler.component.QueryComponent;
import org.apache.solr.handler.component.ResponseBuilder;
import org.apache.solr.handler.component.SearchComponent;
import org.apache.solr.request.LocalSolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class SpellCheckCollator {
	private static final Logger LOG = LoggerFactory
			.getLogger(SpellCheckCollator.class);

	public List<SpellCheckCollation> collate(SpellingResult result,
			String originalQuery, ResponseBuilder ultimateResponse,
			int maxCollations, int maxTries, int maxEvaluations) {
		List<SpellCheckCollation> collations = new ArrayList<SpellCheckCollation>();

		QueryComponent queryComponent = null;
		if (ultimateResponse.components != null) {
			for (SearchComponent sc : ultimateResponse.components) {
				if (sc instanceof QueryComponent) {
					queryComponent = (QueryComponent) sc;
					break;
				}
			}
		}

		boolean verifyCandidateWithQuery = true;
		if (maxTries < 1) {
			maxTries = 1;
			verifyCandidateWithQuery = false;
		}
		if (queryComponent == null && verifyCandidateWithQuery) {
			LOG.info("Could not find an instance of QueryComponent.  Disabling collation verification against the index.");
			maxTries = 1;
			verifyCandidateWithQuery = false;
		}

		int tryNo = 0;
		int collNo = 0;
		PossibilityIterator possibilityIter = new PossibilityIterator(
				result.getSuggestions(), maxTries, maxEvaluations);
		while (tryNo < maxTries && collNo < maxCollations
				&& possibilityIter.hasNext()) {

			RankedSpellPossibility possibility = possibilityIter.next();
			String collationQueryStr = getCollation(originalQuery,
					possibility.getCorrections());
			int hits = 0;

			if (verifyCandidateWithQuery) {
				tryNo++;

				ModifiableSolrParams params = new ModifiableSolrParams(
						ultimateResponse.req.getParams());
				params.set(CommonParams.Q, collationQueryStr);
				params.remove(CommonParams.START);
				params.set(CommonParams.FL, "id");
				params.set(CommonParams.ROWS, "0");
				// creating a request here... make sure to close it!
				ResponseBuilder checkResponse = new ResponseBuilder(
						new LocalSolrQueryRequest(
								ultimateResponse.req.getCore(), params),
						new SolrQueryResponse(),
						Arrays.asList(new SearchComponent[] { queryComponent }));
				checkResponse.setQparser(ultimateResponse.getQparser());
				checkResponse.setFilters(ultimateResponse.getFilters());
				checkResponse.setQueryString(collationQueryStr);
				checkResponse.components = Arrays
						.asList(new SearchComponent[] { queryComponent });

				try {
					queryComponent.prepare(checkResponse);
					queryComponent.process(checkResponse);
					hits = (Integer) checkResponse.rsp.getToLog().get("hits");
				} catch (Exception e) {
					LOG.warn(
							"Exception trying to re-query to check if a spell check possibility would return any hits.",
							e);
				} finally {
					checkResponse.req.close();
				}
			}
			if (hits > 0 || !verifyCandidateWithQuery) {
				collNo++;
				SpellCheckCollation collation = new SpellCheckCollation();
				collation.setCollationQuery(collationQueryStr);
				collation.setHits(hits);
				collation.setInternalRank(possibility.getRank());

				NamedList<String> misspellingsAndCorrections = new NamedList<String>();
				for (SpellCheckCorrection corr : possibility.getCorrections()) {
					misspellingsAndCorrections.add(corr.getOriginal()
							.toString(), corr.getCorrection());
				}
				collation
						.setMisspellingsAndCorrections(misspellingsAndCorrections);
				collations.add(collation);
			}
			if (LOG.isDebugEnabled()) {
				LOG.debug("Collation: "
						+ collationQueryStr
						+ (verifyCandidateWithQuery ? (" will return " + hits + " hits.")
								: ""));
			}
		}
		return collations;
	}

	private String getCollation(String origQuery,
			List<SpellCheckCorrection> corrections) {
		StringBuilder collation = new StringBuilder(origQuery);
		int offset = 0;
		for (SpellCheckCorrection correction : corrections) {
			Token tok = correction.getOriginal();
			// we are replacing the query in order, but injected terms might
			// cause
			// illegal offsets due to previous replacements.
			if (tok.getPositionIncrement() == 0)
				continue;
			collation.replace(tok.startOffset() + offset, tok.endOffset()
					+ offset, correction.getCorrection());
			offset += correction.getCorrection().length()
					- (tok.endOffset() - tok.startOffset());
		}
		return collation.toString();
	}

}
